Print this pageGrowth Rates of Upper Permian Carbonate Platform, Capitan Margin of Northern Delaware Basin
P. M. Harris, G. A. Grover
Subsurface and outcrop studies of the Capitan margin (late Guadalupian,
Capitanian) in the northern Delaware basin have revealed that over 80% of the
total progradation of the margin, over half the total aggradation of the
platform (150 of 290 m), and over two-thirds of the basin fill (190 of 280 m)
occurred during an early 
phase
of development equating with Seven Rivers beds on
the platform. The amount of progradation varied from 6 km from outcrop data in
the Guadalupe Mountains to 19 km along trend to the east from subsurface
information. The later phase of Capitan margin development was coincident with
Yates and Tansil deposition on the platform and was dominated by aggradation and
steepening of the margin.
Corresponding to this two-phase model, two third-order cycles of relative sea
level occur within the Capitanian on the eustasy curve of Ross and Ross: a Seven
Rivers cycle lasting 1.5 m.y. and a Yates-Tansill cycle of 1.0 m.y. Progradation
rates for the Capitan range from 2.6 to 8.3 m/1,000 years. Similar rates are
calculated from high-resolution seismic lines across the Cenozoic margin of
northwestern Great Bahama Bank. Accumulation rates for the Capitan, uncorrected
for compaction, average 125 µm/year and 335 µm/year for the early phase shelf
and shelf margin, respectively, and 160 µm/year and 430 µm/year for the later
phase shelf and shelf margin. These accumulation rates are similar to those of
other ancient, prograding platforms.
By analogy with the Bahamas example and compatible with Permian sea level
curves, the two phases of Capitan growth appear to reflect two cycles with a
rising sea level. A slowly rising sea level during the early phase allowed
significant off-shelf transport of carbonate debris and siliciclastics to
account for the high progradation rates. A faster rate of sea level rise during
the later phase
resulted in less progradation, entrapment of siliciclastics on
the shelf, steepening of the margin, and increased water depth in the basin.
AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.